The X- or Gamma-Ray Energy Absorption or Transfer Coefficient: Tabulations and Discussion

Abstract

The X- or y-ray absorption is closely related to, yet distinct from, the X-ray attenuation coefficient.2 The attenuation is a measure of the number of interactions between incident photons and matter that occur per unit thickness of material traversed. The absorption coefficient, on the other hand, refers to the amount of dissipated by the secondary electrons set in motion as a result of these interactions. Under certain conditions, to be discussed below, the dissipated by electrons in a given volume can be equated to the in that volume. The (also called the absorbed dose)3 is of basic interest in radiation dosimetry because it represents the amount of made available for the production of chemical or biological effects.4 Knowledge of the absorption is essential for estimating the dose, whether it is obtained from a calculated X-ray intensity or from measurements of exposure dose with an ionization chamber. The name energy absorption coefficient is confusingly similar to the names of related quantities defined in the literature and is not really descriptive of its 1 Formerly Rosemary T. McGinnies. 2 Throughout this paper no distinction is made between X- and 7-ray photons, and both are